March 18, 2008 - Gene knockout reduces carcinogens in tobacco leaves.. Scientists have found that the amount of certain carcinogens in tobacco can be reduced by silencing a specific gene in its plant. This may lead to tobacco products with reduced amount of cancer-causing agents, especially smokeless tobacco products (the carcinogens studied are more plentiful in these products). Professor Ralph Dewey and Assistant Professor Ramsey Lewis, both from North Carolina State University, joined hands with researchers from the University of Kentucky to deactivate the demethylase gene function that turns nicotine into nornicotine, which turns into the carcinogen N-nitrosonornicotine (NNN) as the tobacco is cured, processed and stored. Upon comparison with “control” plant lines with normal levels of gene expression, the genetically modified tobacco plants showed a six-fold decrease in carcinogenic NNN, and a 50 percent overall reduction in the class of harmful compounds called tobacco-specific nitrosamines (TSNA) that have been implicated in various cancers in laboratory experiments. In their study report, published online in Plant Biotechnology Journal, Lewis and Dewey say that targeted gene silencing can work as well in the field as it does on the lab bench. It was also found that knocking out the specific gene did not affect the plant’s growth or resistance to insects or disease. One of the authors, Ralph Dewey admits the intent of the work is not to introduce genetically modified tobacco plants. "Once you find a trait of interest, introducing that trait into tobacco varieties that a farmer would grow takes numbers of years," Dewey said.Click on image to enlarge..